Rangers, by virtue of their nature bond, actually gain the ability to call back the spirit and life of an animal companion they have bonded with; it's part of the class description. So, if you bonded scratch, you would be able to call him back to life, as long as he remained your bonded companion.
Where did you get this? According to the beastmaster rules, if the animal dies, you need to spend 8 hours to bond with a new one. You don't rez the one that died.
I played this game out via Tabletop D&D sessions, and during one Scratch did get killed. I simply allowed the players to treat him like any other companion. You can use Revivify scrolls or, if nothing else, pay 200 gold and have Withers, the Talkative Skeleton Guardian of Tombs rez him.
That's how they could do it, but I would hope that they would code the game so that enemies don't target Scratch very much so that players don't have to constantly rez him. That would not be fun.
I do hope they allow this, though. It really would be lots of fun to have either Scratch or the owlbear cub as actual animal companions while adventuring - again, though, only if enemies don't target them much.